Recently, high attention has been widely focused on global environmental issues, and environmentally-friendly motor vehicles equipped with secondary batteries such as electric vehicles and hybrid vehicles have been progressively developed. The motor vehicles often employ a method of converting direct current generated from the mounted secondary battery into alternating current through an inverter, and then supplying required electric power to the alternating current motor to obtain driving force. Electromagnetic waves are generated due to switching operation of the inverter and the like. Since the electromagnetic waves disturb reception of on-board acoustic equipment or wireless equipment or like, countermeasures have been taken to house the inverter or the battery, motor or like together with the inverter in a metallic case to shield the electromagnetic waves (Japanese Patent Application Laid-open Publication No. 2003-285002 A1).
The electromagnetic waves are emitted not only from the motor vehicles but also from many electric and electronic devices including communication devices, displays and medical devices. The electromagnetic waves may cause erroneous operation of precision devices, and an adverse effect on a human body is further concerned. Therefore, various techniques have been developed for reducing the adverse effects of the electromagnetic waves using an electromagnetic shielding material. For example, a copper foil composite obtained by laminating a copper foil and a resin film has been used as the electromagnetic shielding material (Japanese Patent Application Laid-open Publication No. H07-290449 A1). The copper foil has electromagnetic shielding properties, and the resin film is laminated for reinforcement of the copper foil. An electromagnetic shielding structure is also known, in which metal layers are laminated on an inner side and an outer side of an intermediate layer made of an insulating material, respectively (Japanese Patent No. 4602680). An electromagnetic shielding optical member is also known, which comprises a base substrate and a laminated member formed on one surface of the base substrate and composed of a plurality of repetitive unit films comprising a metal layer and a high refractive index layer of niobium pentoxide (Japanese Patent Application Laid-open Publication No. 2008-21979 A1).